1. Field of the Invention
The present invention relates to an apparatus and method for controlling the heart rhythm. More particularly, the invention relates to a magnetic pacemaker or stimulator of the heart capable of pacing the heart without the need for pacemaker leads. More particularly, the invention relates to a pacemaker device in which biphasic pulses of mixed frequencies generate a magnetic field of relatively low density (less than 200 Gauss) capable of stimulating the heart without contacting the heart muscle directly or with the aid of a transvenous lead.
2. Description of the Related Art Including Information Disclosed Under 37 CFR Sections 1.97-1.99
In medicine, electrical impulses are often used to stimulate the heart. Electrical depolarization of the heart has for over 30 years formed the basis for cardiac pacemakers that are used to control the heart rate when the normal intrinsic cardiac pacemaker fails.
To date, all known cardiac pacemakers both implantable and external non-implantable ones use electric pulse stimulation. In the case of permanently implanted pacemakers, the pacemaker is inserted under the skin and the leads (typically silicone or polyurethane coated cables) are inserted into the pacemaker to connect the power source to the heart via the subclavian venous system and the right ventricle.
Numerous problems are associated with implantable pacemakers, with the most notable source of difficulties being associated with the need for surgery to implant the leads into the veins and into the heart. Thus, a substantial advantage would be made available to patients if one were able to pace the heart without using an electrode.
In an effort to remove the need for an endocardial or epicardial lead system, we have developed a unique method using magnetic pulses for non contact cardiac pacing. Previous efforts in the field has been limited to high intensity magnetic field strength, an impractical energy source for implantable pacemakers or even external transthoracic pacemakers. See Irwin, Don D., et al.. "Stimulation of Cardiac Muscle by a Time-Varying Magnetic Field," IEEE Trans. on Mag., Vol. Mag-6, No. 2, June 1970, pages 321-2. That earlier research used magnetic fields to induce an electric field in the cardiac cells but required a magnetic field on the order of 1 kilogauss or more producing a very large bulk effect to simulate the equivalent of an implanted electrode. More importantly, the use of such a strong electromagnetic field can have the serious negative side effect of heating and destroying surrounding tissue as well as the heart itself.
The present invention overcomes the disadvantages of known devices by using a low or medium strength magnetic field (less than 200 Gauss) to directly trigger cell function. The device producing the fields can be completely external to the body or can be placed on or under the skin and does not have any known adverse side effects. It also has the potential for miniaturization and insertion under the skin as a permanently implantable pacemaker without the need for a lead system.